Blowing O-rings, am I doing that?

[PvtStash]

Heyhey, over the last couple weeks I've been losing O-rings after a dive...

I turn off the gas flow (steel lp 80)
purge 2nd stage/octo
disconnect bc inflator hose

and then I take off the 1st stage..., but sometimes it will be difficult, pressure between the 1st stage and the tank valve that when the 1st stage is unscrewed enough will blow out the O-ring, last time I unscrewed it Veerry slowly and the air escaped in a hiss but I still lost the O-ring somehow...

so I'm wondering... is it something I'm doing thats making this happen? or maybe slight imperfections in the O-rings? or is this something that just happens sometimes?

 

[jaybombs25]

you need to completely purge the second stage, make sure all the air is out then unscrew. The residual pressure is causing the O-rings to pop

 

[Jim Lapenta]

You need to purge both stages. I inflate the wing then purge both after turning the valve off. From your description of the problem you still have too much air in the system. Also make sure you are not. tightening the yoke screw too much. Get the wobble out and then maybe a eigth of a turn .

 

[jerry_h]

If the 1st stage is hard to unscrew you probably didn't purge all of the air out, if there is air escaping when you remove the 1st stage you may blow the o-ring also insure that the tank valve is fully closed before attempting to remove the 1st stage.

 

[String]

Try unscrewing it while continuing to hold down the purge (after already clearing it). And as others have said, pure both regs.

Oh and consider DIN so the o-rings wont fly around the room anyway.

 

[redacted]

Remember the holes in the HP port, hose, and SPG spool may be quite small so it can take some time for all the HP gas to drop to ambient. You are purging the LP side of the reg but the HP side is recharging it a bit. I have a couple regs where it may take 30 seconds to a minute to get everything down to ambient. If you get impatient, you risk popping that tank valve o-ring out of place. If you can do it intentionally, it is a good technique to dislodge an old o-ring that needs to be replaced.

 

[sschlesi]

I had a similar experience a couple times. I found the easiest way to be sure that everything is purged is to purge a reg as per normal and then breathe that last bit of air out through a reg. It's obvious when all the pressure is gone when you breathe on it.

 

[spectrum]

Purge it right before breaking the yoke connection. You can have enough air left behind the HP pinhole orifice (in the gauge & hose) to to repressurize the supply side if you give it time and that can disturb the o-ring.

Pete

 

[ClayJar]

All the LP ports are connected through the high-flow internals on the downstream side of the first stage, so there is no reason you'd need to purge in multiple places. Of course, if you *want* to purge both regs just to give them a puff of clean air, that's fine.

Purging two second stages will indeed release the pressure from the LP side of the reg faster (although the difference between something like half a second and a quarter second is negligible in practice). It should be noted, however, that the rate-limiting component is not the release of pressure from the second stage; rather, it is the draining of the "reservoir" of gas on the HP side of things.

This is one of those counter-intuitive situations. You want to release all the pressure, so you purge the LP side. To do a good job, you fully depress the purge, emptying the hoses in no time flat, at which point you release the purge. However, since you were so fast at emptying the LP side, you "finished" purging well before the HP side had drained down through its tiny orifice. Had you purged more slowly, the gas on the HP side would have had more time to bleed into the LP side and be purged, leaving you with less pressure once you release the purge and the system stabilizes.

Purge slowly (but not *glacially*... let's be reasonable :biggrin, and try to purge right before (or as) you unscrew the yoke screw.

(The "breathe on the reg" type of "purging" may work not because you suck more air out of the hoses but because it takes longer, giving the HP side time to bleed down.)

 

[Rick Inman]

A new yoke O ring will take a few dives to get "seated" (meaning stuck) in the orifice. So if you blow one and replace it with a new one, and don't fully depressurize the reg, it will blow a lot easier than one that has some dives on it. The good news is, O rings are cheap and there's nothing wrong with having a new one every dive.

And DIN O rings do sometimes come out, too, and are left behind in the valve opening, but not as often.